Switching device



July 7, 1942. w. J. LEVERIDGE SWITCHING DEVICE Filed May 1s, 1941 m U m M Patented July 7, 1942 SWITCHING DEVICE Walter J. Leveridge, Tuckahoe, N. Y., assignor to Bell Telephone Laboratories,

Incorporated,

New York, N. Y., a corporation of New York Application May 13, 1941, Serial No. 393,163

10 Claims. y (Cl. 20G-112) distinct advantages over solid elements as a con' tact-making medium for electrical circuits. For

instance a body of mercury presents a fresh surface for each successive contact closure and it it not subject to the pitting or corroding effects that gradually reduce the usefulness of solid contact elements. With these advantages in view, several forms of mercury switches have been devised in the past which generally fall into one or the other of two classes. In one of these classes the container is tilted or other-l wise moved to cause the body of mercury within it to shift its position thus opening or closing the desired connections. In the other class an armature or other movable element is forced into a pool of mercury, the free surface of the mercury being displaced into engagement with circuit making contacts. In either case it is necessary to move all or a considerable part of the mercury mass into a position in which it physically engages or disengages the desired ccn-` tact or contacts.

In accordance with the present invention, an armature is movable within a container but is not required to displace a large body of mercury but toy lift only a small amount of mercury to elfect the interconnection of contacts. The invention has been illustrated by several embodiments but in each case the armature is so arranged that it is provided with a small reservoir of mercury of sufficient volume to provide all the mercury that is required for contact 'establishment or a small pool or reservoir of mercury which may by capillary action be fed from a large pool in which the armature rests. Since the amount of mercury carried by the armature in any case is small and the armature itself is of light weight, the amount of energy required to move the armature to its contact closing position is very slight.

For a clearer understanding of the invention, reference may be had to the following detailed description taken in connection with the accompanying drawing in which:

Fig. 1 is a side view partly in cross section 55 of a switching device constructed in accordance with the present invention;

Fig. 2 is a sectional view taken along section line 2-2 of Fig. 1;

Fig. 3 is a side view partly in cross section of another embodiment of the invention;

Fig. 4 is a side view partly in cross section of a further embodiment of the invention; and

Fig. 5 is a side view partly in cross section of a still further embodiment of the invention.

While the invention is not limited to a switch of any given size or proportion it may be noted that switches in accordance with the invention are particularly useful in electrical circuits where relatively small currents are involved, such, for example, as currents of the order generally used in telephone or telegraph systems. For these purposes the switch unit may be made quite small and it should be understood that the figures of the drawing have been made to an enlarged scale to facilitate a clearer understanding of the construction. All of the switch units disclosed are designed for use in connection with a magnetic circuit which may be of any desired type, for example, of the type disclosed in application Serial No. 340,662, of C. E. Pollard, filed June l5, 1940, or of the type disclosed in my application Serial No. 398,538, led June 18, 1941.

Referring first to Figs. 1 and 2 the switch unit comprises a stainless steel or other suitable non-magnetic container I sealed at its upper or open end by a glass bead 2. Sealed axially through th'e bead 2 is a thin-walled sleeve 3 of an alloy which readily seals to the glasss and also sealed through the bead 2 are two lead wires 4 and 5 also of an alloy which readily seals to the glass. Welded to the inner end of these wires are contact portions 6 and 1 which are of a metal wettable by mercury, such as nickel. A soft iron armature 8 is positioned within the container and is of substantially octagonal cross section as best disclosed in Fig. 2, four of the eight faces thereof being narrow as indicated by the numeral 9 to decrease the fric- 0 tional contact area between the armature and the inner wall of the container I. The armature is provided with an axial hole I0 therethrough and the upper surface of the armature is provided with a circular depression Il, the wall of the hole l0 and the surface of the depression being coated nickel or other material wettable by mercury. The other surfaces of the armature and the inner surface of the container are not so wettable. A rod formed of an upper lead wire section I2 and a lower contact similar in cross section to section i3 of a metal wettable by mercury are welded together end to end and inserted through the sleeve 3 and the hole in the armature 8 and then welded to the sleeve 3. The hole l in the armature 8 is filled with a body of mer- CuIy I4.

in assembling the switch unit, the armature 8 is rst inserted into the container l and the bead 2 with the lead wires 4 and 5 and sleeve 3 sealed therein is placed in the upper end of the container and sealed thereto. The container is then evacuated, a measured amount of mercury is placed therein, the container is lled with an atmosphere of hydrogen, and the guide rod is then insertedY through the tube 3 and welded thereto. With theV rod in the position disclosed, the .mercury is forced up through the hole in the armature `and over-I ows into the ldepression Il in the upper surface` of the armature, and due to the fact that the wall of the hole I0 and the surface of the depression l I and the surface of the lower portion I3 of the rod are wettable by themercury,y the mercury will adhere thereto as indicated and any'portion of the mercury which may have entered between the outer surfaces of the armature and the walls of the containerk will' notv adhere thereto but be drawn by` surface tension into the holell) or reservoir within the armature.

When theparmaturev is raised vwithin the container by the'attraction of Va magnetic eld applied to Ythe unit, it'will lift the reservoir. of mercury with it and will engage the mercury which fills the depression H in its upper surface with the lower wettablecontact ends of the lead wires 4 and Y5 thereby interconnecting them through the mercury. When Ythe armature is' released, it will drop into'theV bottom .of the container carrying the mercury with it; thus breaking the connection between the leadv wires 4 and `5`but'due to the fact that the loweror contact 'ends Y6 and 1 of the-lead wires are wetted by the mercury,'small films of mercury will be retained on these ends so that on allV operations subsequent tothe flrst, the elevation of the armature will result in a mer- Vcury to mercury contact between the lead wires 4 and 5.

' The modified form of switch unit disclosed in Fig. 3 is quite similar to that of Fig. l. In this switch unit, the container 2| of stainless steel or other suitable non-magnetic material is tubular and is sealed at its ends Vby glass beads 2l) and 22. The bead 22 has la thin-walled sleeve 23 of an alloy which readily seals to glass sealed axially therethrough and the bead 20 has two lead wires 24 and 25 sealed therethrough, the lead wire 25 terminating just above the inner end of the seal 29Yand serving as a support for the armature 28 and the axially disposed lead wire Z4 having an extension 25 of metal wettable'by mercury such as nickel welded thereto. The armature 28 is the armature 9 of Fig. 1 and has an axial hole'21 therethrough serving as a reservoir for the mercury 29. A third lead wire 30 extends through thersle'eve23 with its upper end slightly above and out of engagement with the `upperrend of lead wire 24 and'is welded to the sleeve 23.

, The switch unit is assembled byrst inserting the armaturel 28 into the-container and then sealing the beads 2i! and 22 (with the lead Wires and sleevesealed therethrough to the ends of the container. The container isV then evacuated, a

measured amount of mercury is` placed therein, the container is thenlled with an Yatmosphere of hydrogen and the lead Ywire 33 is nally inthe armature into bridging engagement between the ends of the lead wires 24 and 33. The switch unit, therefore, functions as a simple contact transfer. To insure a mercury to mercury contact after the initial operation of the unit, the

contact` end 3l of lead wire 39 and the contact end32 of the lead wire 25 may be made of a metal wettable by mercury such as nickel and welded to the ends of such wires.

The modified form of switch unit disclosed in Fig. 4 comprises a container 33 of stainless steel er other suitable non-magnetic material, the upper or open end of which is closed by a closure comprisingV a glass bead 34 sealed to a ring 35. The ring 35 has such an outside diameter that it may be seated. on thev inner` shoulder of the flanged portion 3B ofthe container 33. Extending through the glass bead 34 are three lead wires 31, 38 and 39 which terminate justY below the inner surface Vof the bead 34. Spot welded to the inner endsfoftthe wires 31 and 38'are contact portions 40 and 4| made of a metal easily wettable by mercury, as for example nickel, and welded to the inner end of the axially disposed wire 39 is a portion 42 of nickel which extends to the bottom of the container 33 and is seated in a central hole in the stainless steel disc 43 positioned in the bottom vof the container. The portion 42 is thus axially positioned within the container .and serves as aguide rod for the armature assembly44.

The armature assembly comprises a central nickel tube 45 having an inner diameter slightly greater than the diameterV of lthe rod 42 and having an inner lflanged portion 45 and an upper anged portion 41, a depending cup-shaped member 43 also of nickel and a permalloy armature disc 49. The base portion of the member 48 and the armature disc 49 are assembled on the upper end of the tube 45 after the inner flange 45 is formed on the tube and then held in place thereon by spinningV the outer flange 41 down upon the upper surface of the armature disc.

rThev outer edge of the armature disc 49 is upturned at 59 and the upper surface of the armature .is preferably coated with a material easily wettable by mercury, for example, coated with nickel. The depending wall of the member 43 is cut away at diametrically opposite portions thereof as indicated at 5Il and the lower edge-of the member is normally partly submerged in a pool of mercury 52 located in the bottom of the container 33.

Due to the capillaryaction between the outer surface ofthe guide rod 42 and the inner surface of the tube 45 some of the mercury is conducted upwardly to ll the space between the tube and guide rod and to form an auxiliary pool upon the upper surface of the armature disc 49.

In assembling the switch unit, the lead wires 31, 38 and 39 are sealed into the glass bead 34 and the bead 34 is sealed within the ring 35'to form the closure assembly. The disc 43 is then inserted into the bottom of 'the .container 33,

` the required amount'ofrmercury is then placed in the container, and the armature assembly 34 is then placed within the container resting in the mercury. The enclosure assembly is then placed in position with the guide rod extension 42 of the lead wire 39 extending through the tubular portion 45 of the armature assembly into the central hole of the disc 43 and the lower edge of the ring of the closure assembly seated in the shoulder of the flanged portion 46 of the container. The assembled switch unit is then evacuated and refilled with hydrogen after which the closure assembly is sealed to the flange of the container by plastic material placed at the junction point 53.

In the operation of this switching unit when the armature is raised within the container by an external magnetic eld, it will lift the small pool of mercury carried upon its upper surface into engagement with the contact ends and 4| of the lead wires 3l and 38 thus interconnecting f such lead wires 01 connecting both of such lead wires to the central lead wire 39. When the armature is released, it will be drawn towards the bottom of the container 33 by the surface tension of the mercury pool 52 acting upon the outer surface of the tubular portion and upon the surfaces of the skirt portion of the member 48 of the armature assembly thereby disconnecting the lead wires 3l, 38 and 39 from each other. Small films of mercury will be retained on the contact ends 4l) and 4I of the lead wires 31 and 38 so that after the rst operation of the switch unit, the lead wires will be interconnected through a mercury to mercury contact upon each subsequent operation of the unit.

The modified form of switch unit disclosed in Fig. 5 comprises a container 54 of stainless steel or other suitable non-magnetic material having an upper flanged portion and to the upper edge of which is sealed a glass rim 55. Seated on the inside shoulder of the flanged portion 55 is a disc 5l of suitable insulating material, such as Lavite, through which extend two flanged contact members 5tand 59, preferably of a metal wettable by mercury such as nickel, and a centrally disposed lead wire 60. Welded to the outer or anged ends of the contact members are two lead wires 6| and 62. The lead wires 60, 5l and 62 are all of a material which may be readily sealed to glass. ner end of the lead wire 6l) is a guide rod 63 of stainless steel, preferably nickel plated. the lower end of which extends through an axial hole E4 in the bottom of the container and is welded therein. The rod 63 serves as a guide for the armature assembly 65.

The armature assembly comprises a central tubular portion having an inside diameter slightly larger than the diameter of the guide rod and an upper flange $1. Preferably it is made of nickel and thus wettable by mercury. Welded or otherwise secured to the under-side of the flange 6l is a hollow cylindrical iron armature 68, the upper end wall of which is secured to the flange 6l, the cylindrical wall of which is disposed for free sliding movement with respect to the inner surface of the container 54 and the lower end wall of which is provided with a large opening 69 to permit mercury from the pool '1B deposited in the bottom of the container to enter into the armature. Some of the mercury from the pool 10 is drawn upwardly between the inner surface of the tubular portion 66 of the armature assembly and the guide rod 63 to form a Spot welded to the iniii) shallow pool upon the upper surface of the flange 61 as illustrated.

In assembling this switch unit, the required amount of mercury is first placed in the bottom of the container and the armature assembly 65 is then inserted into the container resting in the mercury pool l0. The supporting disc 5l with the lead wires 60, 6| and 62 with their guide rods and contact extensions assembled therein, is then inserted to rest on the shoulder' on the ange portion 55 of the container and the ends of the guide rod 63 where it extends through the hole in the bottom of the container are welded thereto. The glass rim 56 is then fused to the upper edge of the container 54 and the glass tube l! is then inserted between the rim 56 and the lead wires 6| and 62 and the glass tube 12 is placed around the lead wire 60. The switch unit is 'then evacuated, fillled with hydrogen and finally sealed by fusing the glass tube ll to the rim 56 and fusing the glass tube l2, the fused glass thereby flowing around the wires 65, 6| and 62 and sealing them to the glass thereby completely sealing the unit. The unit functions in the manner described in connection with the unit disclosed in Fig. 4.

It will, of course, be understood that the invention is not limited to the particular structures used to illustrate it in the present disclosure. If desirable the container might be made in various shapes and sizes and of other material such as glass, The armature may vary in shape and proportion, the shape and location of the contacts may also be varied and the switch unit may be adapted for use in various types of magnetic circuits.

What is claimed is:

1. A mercury switch comprising a container, an armature movable within said container having an axial hole therethrough, the wall of said hole being of a material wettable by mercury, a column of mercury held within said hole. and terminals interconnectable by said mercury upon the movement of said armature within said container.

2. A mercury switch comprising a container, a guide rod axially positioned in said container, an armature movable within said container and having an axial hole therein through which said guide rod extends, the wall of said hole being of a material wettable by mercury, a column of mercury held by surface tension within said hole between the wall thereof and said guide rod, and terminals interconnectable by said mercury upon the movement of said armature within said container.

3. A mercury switch comprising a container, a guide rod axially positioned in said container, an armature movable within said container and having an axial hole therein through which said guide rod extends and having a depression in the upper surface thereof, the wall of said hole and said depressed surface being of a material wettable by mercury, a column of mercury held by surface tension within said hole between the wall thereof and said guide rod and forming a` shallow pool in the depression in the upper surface of said armature, and terminals interconnectable through the mercury of said pool upon the movement of said armature within said container.

4. A mercury switch comprising a metal container, a glass bead for sealing the open end of said container, a metal tube sealed axially through said bead, a lead wire extending through said tube welded thereto and having a contact portion wettable by mercury, an armature movable within said container and having an axial hole therein, the wall of said hole being of a material wettable by mercury, a column of mercury held within said hole, and other lead wires having contact portions wettable by mercury and connectable with each other and with said rst lead wire by said mercury upon the movement of said armature within said container.

5. A mercury switch comprising a metal con tainer, a glass bead for sealing the open end of said container, a metal tube sealed axially through said bead, a plurality of lead wires sealed through said bead and having contact portions on their inner ends wettable by mercury, a guide rod extending through said tube rand welded thereto, an armature movable within said container and having an axial hole therein through which said guide rod extends, the wall of said hole being of a material wettable by mercury, and a column of mercury held by surface tension within said hole between the wall thereof and said guide rod, said lead wires being interconnectable and connectable with said guide rod upon the movement of said armature within said container.

6. A mercury switch comprising a container, a guide rod axially positioned in said container, an armature assembly movable within said container comprising a central tubular portion surrounding said guide rod and having an inner surface wettable by mercury and a portion of magnetic material secured thereto, a pool of mercury in the bottom of said container andV extending through the space between said guide rod and the inner surface of said tubular portion to form a shallow auxiliary pool upon the upper surface of said armature assembly, and terminals interconnectable by the mercury of said auxiliary pool upon themovement of'said armature assembly within said container.V

'7. A mercury switch comprising a metal container, a glass bead for sealing the open end of said container, a guide Vrod sealed in saidbead and extending axially to the bottom of said container, an armature assembly movable within said container comprising a central tubular portion surrounding said guide rod having a flange upon its upper end, said tubular'portion being of a metal wettable by mercury anda portion of magnetic material secured to said flange', a pool of mercury in the bottom of said container and extending through the space between said guide rod and the inner surfaceof said tubular por tion to form a shallow auxiliary pool upon the upper surface of said armature assembly, and lead wires having contact portions of a metal wettable by mercury sealed through said bead and connectable with each other and with said guide rod by the mercury of said auxiliary pool upon the movement of said armature assembly within said container.

8. A mercury switch comprising a metal container, a glass bead for sealing the open end of said container, a guide rod sealed in said bead and extending axially to the bottom of said container, an armature assembly movable within said container comprising a central tubular portion surrounding said guide rod and having a flange adjacent to its open end, an inverted cupshaped portion having an opening in its base through which the upper end of said tubular portionY extends, said tubular portion and said Vcup,- shaped portion being of a material wettable by mercury and a disc of magnetic material having an upturned edge and having an opening in its base through which the upper end of said tubular portion extends, said cup-shaped portion and said disc being clamped to said tubular portion between said flange and a second flange spun over from the upper end of said tubular portion, a pool of mercury in the bottom of said container into which the tubular portion and the side wall of said cup-shaped portion extend, said mercury extending through the space between the guide rod and the inner surface of said tubular portion to form a shallow auxiliary pool upon the upper surface of said armature assembly, and other lead wires having contact portions of metal wettable by mercury sealed through said bead and connectable with each other and with said* guide rod by the mercury of said auxiliary poolupon the movement of said armature assembly within said container.

9. A mercury switch comprising a metal container, a disc of insulating material supported in the upper end of said container, a guide rod extending axially through said disc to the bottom of said container, lead wires having contact portions of a metal wettable by mercury supported by said disc, a glass bead for sealing the open end of said container and for holding said disc in position, an armature assembly comprising a central tubular portion surrounding said guide rod having a flange upon its upper end and being of a material wettable by mercury and a portion oi magnetic material secured to said iiange, and a pool of mercury in the bottom of said container and extending through the space between said guide rod and said tubular portion t0 form a shallow pool upon the upper surface of said armature assembly, whereby said lead wires are connected together and with said guide rod by said auxiliary pool of mercury upon the movement of said armature assembly within said container.

l0. A mercury switch comprising a metal container, a glass bead for sealing the upper end of said container, a guide rod extending axially through said bead to the bottom of said container, lead Wires having contact portions of a metal Wettable by mercury sealed through said bead, an armature assembly comprising a central tubular portion surrounding said guide rod having a flange upon its upper end and being of a material wettable'by mercury and a hollow cylindrical armature portion of magnetic material secured by its upper base to the flange of said tubular portion and having openings in both of its bases through which said tubular portion extends, the opening through the lower base being sufliciently large to permit the penetration of mercury within said cylindrical armature portion, and a pool of mercury in the bottom of said container and extending through the space between said guide rod and said tubular portion to form a shallow auxiliary poolY upon the upper surface of said armature assembly whereby said lead wires are connected together and with said guide rod by said auxiliary pool of mercury upon the movement of said armature assembly within said container.

WALTER J. LEVERIDGE. 

